Butanol is an important industrial chemical, useful as a fuel additive, as a feedstock chemical in the plastics industry, and as a food grade extractant in the food and flavor industry. Accordingly, there is a high demand for butanol, as well as for efficient production methods. One production method which has the potential to reduce environmental impact includes the production of butanol utilizing fermentation by recombinant microorganisms.
Maximum butanol production will require optimization of the recombinant microorganism comprising a butanol biosynthetic pathway and optimization of the process by which butanol is produced. Growth of the recombinant microorganism in different stages of the process is critical for the butanol process. The three phases (e.g., (1) the growth phase, (2) the propagation phase, and (3) the production phase) of the process have different operating conditions, which results in different physiological states for the recombinant microorganism. Pathway leakage and accumulation of inhibitory intermediates can limit growth rate and limit maximum cell density achieved at each stage. An intricate combination of genetic and process solutions to achieve the desired overall volumetric productivities would represent an advance in the art.